Abstract:
This study analyzed the scope effects of respondent uncertainty in contingent valuation
(CV) by evaluating whether willingness to pay (WTP) estimates were sensitive to
changes in the magnitudes of motorized emission reductions in the city of Nairobi,
Kenya. The WTP estimates were elicited through the conventional payment card (PC),
stochastic payment card (SPC) and the polychotomous payment card (PPC) formats.
While SPC and PPC formats were used to capture respondent uncertainty, the PC
format captured respondent certainty regarding the amounts individuals were WTP for
emission reductions. Based on parametric and nonparametric analysis, results show that
certain (PC) respondents stated significantly larger WTP amounts for larger emission
reductions than for smaller reductions. Conversely, uncertain (SPC and PPC)
respondents stated smaller amounts for larger emission reductions than certain (PC)
respondents. The implication is that though respondents were sensitive to the scope of
motorized emission reductions, respondent uncertainty lowered their sensitivity to scope.